my first CB200 top end teardown and many questions...

vinty200

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Hi Everyone,

This is a continuation of multiple separate posts I've made over the last year or so related to:
1) low compression, 2) bike dying at stop when engine was hot, 3) disparity in cylinder temps not fixable with carb adjustments, and 4) engine noises at idle.

After trying each of the easy fixes suggested by all the guru's here, I wasn't seeing much change in the bike's behavior. One common suggestion previously was to address the compression problem... so I broke it open today to investigate further.

The engine has 10k miles. it was given to me in pieces as a project bike.
PO said it had been sitting for 10years with unknown engine condition.
this is my first bike, and I have MANY questions for you all:

Regarding Noises at Idle:
I think it was ancientdad who suggested a loose/malfunctioning tensioner spring, and he was right.
I was never able to get it to tighten up externally.
Inside, the chain looks like it has been grinding into the cylinder head, with a deep enough gouge that it appears to be binding the spring mechanism.

pretty sure this tensioner mechanism needs replacement, correct?

Also, assuming I am able to deburr the hole that the tensioner spring is sitting in (that is causing sticky behavior) do I need to address the ground-away & missing material caused by slack chain hitting the head? or leave it?
tensioner2.jpg


Also, how typical is this tension mechanism idle sprocket wear?
The nubby teeth here looks like it needs replacement, but I'm not sure how tall they are supposed to be. thoughts?
spring tensioner roller.jpg


Cylinder head has dark stain near Left Cylinder (top of the photo below). Does that suggest headgasket blowby?

And what is going on with Right Cylinder exhaust valve tan coloring? is this evidence of overheating?
Its worth noting was that this was always the "hot" cylinder... 30-40deg F higher than Left.

head.jpg

Regarding Compression - the cylinder walls are rough on both. I assume this was the source of bad compression although I was expecting much much worse given the atrocious compression readings (~100-110 psi). note, the lighting in the image makes it look much rougher than reality. I will try honing first, i think.

cylinder.jpg

Rings are intact / not broken. Pistons appear fine.
Other than dimensional checks called out on each in the FSM, what else should I look for to determine if they need replacement?

I know that's a lot all at once!... but as usual - thank you for your help!
 

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The condition of the pistons is irrelevant at this point, the cylinders have rust rings from hell and that is likely why the compression was so low. You'll need to go at least 2nd oversize on the cylinders (0.50mm), maybe more, to get that cleaned up. It probably sat for a very long time somewhere along the way before you got it, got stuck and was later unstuck and revived but not rebuilt. The valve color probably relates to that cylinder running better than the other one. As for the cam chain wear - ugly for sure - once you get it completely apart and clean you can inspect the area to be sure it didn't get worn all the way through into either the passage for the cam chain adjuster rod or the outside which would present an oil leak. Oh, and the cam chain tensioner roller is shot but the little nubs are not the worst part, it's the caved-in look of the rubber roller elsewhere from getting pummeled by the loose chain.
 
As AD noted lots or worn out parts in there. I had some of the same wear on the tensioner and associated parts on my CL175. If your going to do it right it needs everything that is part of the cam chain and tensioner system replaced. That means the lower rubber roller the cam chain first hits when leaving the crankshaft below your tensioner picture. The tensioner teethed roller and the complete pusher rod assembly and that spring for sure. A new cam chain is a must too, as it has been hitting the barrels side per the gouges.That deep gouge is typical of no maintenance by a PO letting the cam chain run too slack.

You can use some high temp JB Weld to rebuild that worn area in the cylinder wall which will strengthen that part, as the slider rod of the adjuster runs through there. Honing will not fix that cylinder issue and OS pistons may be available from a British supplier IMD pistons, if you can't find any OEM NOS Honda ones.

A valve job with attention paid to the thickness of the valve side faces, as with time they tend to wear quite thin over time. A lapping will not work well if they are badly worn away. All these parts should be available, yet it starts to add up $$$ doing a rebuild of these worn parts.
 
These are pictures of a brand new 175 cam tensioner assembly. Not quite the same as the CB200, but principal is the same, this is what the tensioners wheels should look like.

The toothed wheel is pretty much unobtanium, unless you get lucky and find a complete NOS tensioner assembly. Capellini do a replacement steel wheel with needle roller bearings, at a price. :shy:

jTeEtHx.jpg


jbitd9B.jpg


70ZQapT.jpg


0bLbrF8.jpg
 
Richard, will the CL175 tensioner assembly work in his CB200 motor. Since CNSNL has the complete assembly still available for the CL175 at a decent price.
 
Flyin900 said:
Richard, will the CL175 tensioner assembly work in his CB200 motor. Since CNSNL has the complete assembly still available for the CL175 at a decent price.
Click to expand...

No, the actual pressed metal frame of the CB200 tensioner is longer, also the rubber idler wheel is larger. The idler wheel was available from David Silvers last time I looked. I suppose at a pinch one could buy the 175 part and transfer the toothed wheel across, although that would not be straight forward, as Honda fixed the wheel in place by riveting over the central axle.
 
The last pic in Vinty's #1 post shows a compressed pushrod. The tensioner then never had a chance to do it's job. Hard to see much of the tensioner yet, wait till it's out and inspected before deciding it must be replaced. If the pad that the push rod pushes on, on the other end of the tensioner is solid, and the nubby roller is not breaking down, I'd get a new chain and push rod and spring if needed and go with it. Other tensioners don't even have the knobby wheels, like the 160's, 305's so I wouldn't worry on that if the rubber is still intact and somewhat supple.

Stuck push rod looks to me like the culprit and possible miss route of the cam chain as well because the chain should never have been that close to the front tunnel wall unless the chain was outside (or front) of the push pad of the tensioner. It will be evident when the tensioner is removed and chain wear is seen on the outside or front of the push pad. The more I think about it that would also explain the stuck push rod because the chain would prevent the rod from pushing on the pad.
 
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That wear in the CB200 head is typical of a very slack but correctly routed cam chain.

Differences in the 175 and 200 parts:

CB200 tensioner on the right side of this photo, 175 on the left.

gdFMfww.jpg
 
Waiting to see if wear on the outer edge of the push pad on the tensioner. With that much extreme wear on the inside of the rod, it wouldn't surprise me.

I know I don't have anywhere near the experience that a lot of guys here do, but I'm just thinking and watching. Being a bonafide victim of incorrect PO assembly, myself.
 
Yes my CL175 I did exhibit those same marks on the barrels, yet not as bad as the posters's part. It is a sign of no maintenance, or lack of cam chain tensioning. The issue is most of those wear items are 50+ years old and the rubber is like a hockey puck hard and fragile. Eventually there will be no choice but to reuse, or buy used parts for many of these bikes. I did a quick search for the parts he may need and most items are already gone from the key suppliers, with some items available if your willing to buy at top dollar from various vendors for additional shipping expenses.

A case in point is the 219/82 link cam chain he will need. Many are still available in a endless loop or a peen style link, although very few in this last style. The chains from RK and DID with a removable split link are pretty well gone now. I searched for a friend yesterday for his CB350F motor rebuild and came up dry for this style. He doesn't want to split the cases, yet that is likely the route he will need to go now.
 
My concern is the depth of the wear on the head. Roughly looks like 50% of that area is worn away and since it a structural area supporting the chain tensioner I'm concerned it might break loose with the pressure of the lock bolt pushing on the shaft.
 
Jim as noted above in my post that area can be strengthened/rebuilt with a JB Weld metal epoxy that will reinforce it more than adequately. I agree that it is probably very close to wearing through into the tunnel of the adjuster rod. I did the same repair on my CL175, yet it wasn't worn as badly as that one. I like the Tech Steel metal epoxy as you know, since I feel it is a superior product to the JB Weld, yet it may not be as easily obtainable as the JB products in the USA.
 
Flyin900 said:
Jim as noted above in my post that area can be strengthened/rebuilt with a JB Weld metal epoxy that will reinforce it more than adequately. I agree that it is probably very close to wearing through into the tunnel of the adjuster rod. I did the same repair on my CL175, yet it wasn't worn as badly as that one. I like the Tech Steel metal epoxy as you know, since I feel it is a superior product to the JB Weld, yet it may not be as easily obtainable as the JB products in the USA.
Click to expand...
I saw that but I'm still not sure that would be adequate, welding would for sure. Looks like Tech Steel might be available thru CarQuest or Napa stores.
 
Thanks all for the feedback. Really helpful. I'll keep you posted after I clean it up.

Sent from my GM1915 using Tapatalk
 
old thread, i know, but I'm just closing it out with conclusions after teardown. ballbearian was correct - the chain had been dragging and digging into the side of the head so much that a burr got generated at the top of the tensioner hole and that kept the rod from sliding up and down.

the chain was routed correctly but banging against everything. lots of debris everywhere.

i was able to deburr the damaged hole and also confirmed the chain damage did not extend into the hole but the whole thing was so ugly i decided not to bother trying to resurrect it.
i found a used head from a junkyard and started again from there. images below show original damage a little better, including the wear to the sprocket tensioner, also later replaced.

IMG_20230804_144456.jpg IMG_20230804_144521.jpg IMG_20230804_144816.jpg
 
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